An Australian ultra-marathon swimmer forced to abandon her attempt to swim from Cuba to Florida because of debilitating jellyfish stings said Thursday she won’t try it again.

Chloe McCardel abandoned her bid to make what would have been a record-breaking swim Wednesday night. She got in the water at 9:59 a.m. Havana time on Wednesday, hoping to become the first person to swim from Cuba to the U.S. without using a shark cage or wetsuit.

Diana Nyad Ends Latest Cuba-to-Florida Swim Attempt

Diana Nyad swam a ceremonial final leg to shore in Key West Tuesday afternoon after ending her latest attempt to swim from Cuba to Florida earlier in the day. As soon as she walked onto the sand, a welcoming committee gathered on the beach sang "Happy Birthday" to Nyad, who turns 63 on Wednesday. She expressed a bit of disappointment about failing to make her complete, ambitious journey, but said she got a life lesson out of it. (Published Tuesday, Aug 21, 2012)

The 28-year-old swam nonstop for 11 hours, but jellyfish then stung her around her neck, arms, back, mouth and tongue, her representatives said in a statement Thursday. After receiving the “severe and debilitating jelly fish stings,” there was concern about swelling affecting her ability to breathe efficiently, and her swim was cut short.

"I had one coming out of my mouth. I was pulling it, this tentacle out of my mouth, but I don't remember this moment,” McCardel told The Associated Press. “My kayaker told me that I was doing this, 'cause I have no recollection. I'm not coming back. That's it.”

Diana Nyad Plows Through on Third Day of Cuba-to-Florida Swim

Diana Nyad slogged across the Straits of Florida for a third straight day Monday, hopeful she could fend off hypothermia, jellyfish and stormy weather as she inched toward a swimming record. (Published Tuesday, Aug 21, 2012)

During a sometimes tearful news conference in Key West Thursday, McCardel explained why she won't make another attempt to swim across the Florida Straits.

"It's really important to me to stick to traditional marathon swimming, so most people just call it English Channel rules — bathers, goggles and cap — and what I went through kind of magnified and exemplified that it's not possible to swim those conditions in these waters," she said.

Completing the journey of about 110 miles across the straits could have taken as long as 60 hours. McCardel, who has swum across the English Channel six times, trained for the past nine months for the Cuba-to-Florida effort.

“Obviously after so much planning and preparation, it’s disappointing,” McCardel’s husband, Paul McQueeney, said in the statement. “But Chloe’s safety always is the number one priority, so when the decision had to be made, there was no question that she needed to pull out.”

One of her support vessels took her back to Key West. McCardel said the trip was excruciating.

"It was two and a half hours of the worst pain, continuously, every second, of my whole entire life. It's like fireballs in every fiber," she said.

She will remain in Key West for a short time until she feels comfortable to travel home.

McCardel said she chose June for her swim because the jellyfish danger was supposed to be low. But she found herself in a swarm.

"I got smashed with them coming from every direction," she said. "I would not have gone to all this trouble if I had known they would be out in such numbers in June."

Three women have undertaken a total of five attempts to traverse the Florida Straits over the past three summers, but none have made it. Jellyfish stings and strong currents have been the main obstacles.